Sunday's Westworld episode -- the sixth in the season -- follows Caleb and the smart, distrustful and foul-mouthed rebel known as "C."

We last saw these characters in episode 4, the head-spinning installment that caught Maeve and Caleb (now a host) up to the timeline Bernard and Stubbs have been traveling in this season. We also learned C is the grownup version of Caleb's beloved daughter, Frankie.

In the latest episode, C weeds out an imposter planted by Chalores, and Caleb points some razor-sharp words at the host-in-chief. Still, it seems like the good guys have cleared very little ground in toppling Chalores' evil empire. (She still commands an entire city's worth of humans, and holds sway over hosts like William.) Given that Caleb is locked in a waking nightmare, it looks like it will be up to C, Maeve, Bernard (and maybe Christina?) to do something about it.

Here's what else you need to know about episode 6. Only two episodes are left in the season… I'm nervously eyeing the hourglass.

J's backstory

Given all the timeline-switching, it took my brain a minute to adjust to this week's opening scene. Ah, this is the real-kid Frankie -- not the fake one. It's a flashback, OK.

The show opens with a teenager sitting near a playground on a bench. Young Frankie walks up and leads him to Uwade, Caleb's wife. It's revealed that the teen is the young version of J, and his brother has vanished. Uwade says nothing can be done for his brother -- an outlier taken by Chalores crew. She and Frankie are there so J doesn't meet the same fate. (Last week, Chalores explained her sound manipulation doesn't work on some humans. She's not surprised there's some "spoilage in the crop," but it's causing some big problems for hosts.) Some drone hosts show up and the group narrowly escapes, minus one of Uwade's allies, who gets caught. 

Chalores is looking for answers

Chalores is still searching for an answer to her host/outlier problem -- nearly 40 hosts have killed themselves after interacting with outliers, and the risk to her people continues. Chalores is a nickname for Charlotte Hale. In the past, Dolores made copies of herself -- the "self" that exists in her pearl -- and put one into a host version of Hale.

Chalores asks Caleb (a host version of him) how outliers are making hosts take their own lives. She brings up a scene in episode 4, when human Caleb fights off her parasite, telling her he "had something" she didn't. Chalores wants to know what enabled him to resist her, and Caleb won't give it up.

A frustrated Chalores leaves, but not before telling Caleb that Frankie is alive. She also tells him he's in a "temporary" host body that won't last much longer.

Rebooting Maeve

When we last saw Bernard and C/Frankie, they had just pulled a dilapidated-looking Maeve out of the desert. In episode 6, Bernard and C pay a visit to the '20s theme park to revive her. (It's abandoned, far from the lively place Maeve and Caleb occupied two decades ago.) Bernard starts to poke around the park for "supplies" to get Maeve up and running again, and C, who hasn't yet caught on to his identity as a host, becomes suspicious.

Bernard says Maeve's time in the ground corrupted her control unit. He pries another one out of a random host's head. Bernard reveals to C that Chalores needed to understand human minds, so she collected data from people who visited the park. But instead of using cowboy hats like Delos did, she used… scanners hidden behind mirrors? That's what it looks like to me, at least. Bernard says mirrors worked because they played off the basest human impulse: vanity.

Bernard opens up a mirror and tells C to take a look, and a machine scans her. He takes something that looks like a chip from the machine and sticks it in a device he's holding. C asks what he's up to, and he says what he grabbed will help speed up Maeve's data transfer. (Hmm, seems a little suspicious.) For the actual transfer, a cord connects Maeve's control unit and the random host's control unit. Anticipating the return of C's friends, Bernard hides Maeve's control unit inside a piano.

An imposter in 'the cause'

Earlier, during Chalores' tense talk with Caleb, she tells him that she sent a "visitor" Frankie's way. My mind immediately went to the two goons Bernard took out at the diner a few episodes back. But as the episode continues, it becomes clear she has something else in the works.

When C's allies return, they tell C that they suspect a spy is among them. Without warning, C suddenly shoots Bernard, identifying him as the "mole." She says, "the park was designed to collect data from guests," and Bernard is trying to copy all of them. Stubbs is perplexed. The only thing Bernard says in his defense is "it's complicated." What could he have up his sleeve?

A little while later, a restrained Bernard tells C that one of her friends isn't who they claim to be. "Your team went into the heart of Hale's city, but one of them didn't come back," he says. Bernard's prophetic abilities aren't able to reveal who the imposter is.

C locks her girlfriend, Odina, in a room, unable to tell if she is the hidden host. But it turns out to be J. C realizes the truth when "J" tells her that she's like a sister to him. At the beginning of episode 6, when C/Frankie appears as a child, she attempts to contact Caleb via radio. J's in the room too, and hears Frankie tell her dad she always wanted a brother. Teen J, clearly still hurt by the news about his own brother, rejects the term.

C shoots the host version of J, but it's not enough to take him down. Host J presses her to tell him where Maeve's control unit is. She tells him she stashed it… behind him. He turns around, and we see Maeve -- reanimated -- stab him in the head.

Westworld cranks up the horror

While Bernard and C are busy bringing Maeve back/spotting camouflaged enemies in the desert, Caleb is starring in a horror movie. When Chalores leaves Caleb in his cell, things get dark. We see more host versions of Caleb are locked in the cells around him. One Caleb has horrific marks on his face, which appear to be the result of staying in a decaying host body for too long.

Caleb looks inside of an hourglass in his cell, and finds a tiny metal object. He presses down on it, and it exposes a needle, which pricks him. Things start to get blurry. The next thing Caleb knows, a drone host has decided to torch the room with him still inside. Caleb yanks a vent on the ground until it opens. (A small arrow etched into it instructs him which way to pull it.) He lands in a pit of ash… which he seems to register as being from the bodies of other Calebs.

From there, the nightmare continues. Caleb faces off with a drone host, eventually stabbing him pretty nastily in the head. Following a trail of bloody handprints -- presumably left by other host Calebs who braved an escape -- he crawls into a ceiling vent. Then things get really gruesome. Caleb reaches the end of the vent maze and finds that there's a brutal drop to the floor below. Two Calebs lay dead on the ground beneath him. (Sheesh, Westworld, this is some pretty sick stuff.) There's a Caleb still in the vent with him, clinging to life, and he tells the main host Caleb to use his body to cushion the fall. Caleb does this, and survives the jump. He then stumbles out onto a rooftop.

Violent ends

Using some tech on the roof, Caleb leaves a message for Frankie. He tells her that "it has to be her" (seems like some serious foreshadowing to me). We see that C/Frankie heard a bit of the message, and knows that her dad is alive (well, at least in some capacity). Chalores appears and tells Caleb she crafted his recent harrowing experience, planting the needle so he'd have a "little hope," and possibly show his cards. But she didn't gather much from Caleb's message to Frankie.

Caleb fires some verbal arrows at Chalores, telling her with struggling breaths that her hosts would rather die than live in her world. "They're not infected," he says. "They're just trying to get away from you." It hits a nerve with Chalores, who angrily snaps his neck.

C is for Cookie… 

When Caleb leaves his message for Frankie, he starts off with her nickname, Cookie. Could this be why the rebel goes by C?

Stray thoughts

• After seeing Uwade as a rebel during a flashback, we learn from C/Frankie that she got very sick. That, coupled with her absence in adult Frankie's timeline, seems to suggest she passed away.
  
• The famous Westworld "pearl" is inside those lightbulb-shaped objects in the episode.
  
• I'm not sure if the "outliers" this season are meant to be the same people referred to as "outliers" last season by Engerraund Serac/Rehoboam. (In season 3, Serac sees unpredictable humans as "outliers," a threat that must be dealt with.) It seems to me like the word is being reused now to describe a different set of people. But this is Westworld... Are there ever those kinds of coincidences?
  
• Maybe it's too straightforward a guess, but I've been assuming love for his daughter is what allowed Caleb to defy Chalores. Earlier in episode 4, as part of her explanation for why she once slipped out of Caleb's life, Maeve tells him that she "wanted him to have something to fight for," clearly talking about Frankie. Seemed like an important nugget to me.